1. Field of the Invention
The invention relates to a method of producing juice concentrates and juice aroma concentrates.
2. Description of the Prior Art
The standard method of producing natural fruit and vegetable juice concentrates is by means of distillation using temperatures of between 80 and 150.degree. C. However, since most flavour and aroma molecules are heat-sensitive and volatile, use of such high temperatures may result in degradation or total loss of the juice flavours and aromas which the process is aiming to recover and concentrate.
Many of the volatile, but very desirable, juice flavours and aromas are taken off in the distillate (the juice water phase) and it is known to concentrate this water phase, usually by fractional distillation, in order to obtain what is known as a `juice aroma concentrate` which may then be used, for example, as a flavouring in the food processing industry.
Although distillation is the standard method of producing these concentrates, a process known as reverse osmosis has also been proposed. In this process, the juice or juice water phase to be concentrated is passed over a semi-permeable membrane under pressure to `squeeze out` the water from the mixture leaving behind a concentrated solution containing the flavours and aromas.
The applicant has found that one problem with known reverse osmosis methods is that the high pressures used, i.e. above 50 bar, may adversely affect the delicate flavour and aroma molecules so that the concentrate obtained no longer resembles the original starting material. In addition, use of high pressure results in increased temperatures which is also disadvantageous as explained above.
It is an object of the present invention to provide a method of producing improved juice concentrates and juice aroma concentrates.